Your S may not be as exposed to it as you think. My H is terrible with ME, but was careful not to do it around my S. Not that your S can't pick it up--I think my (and he's now 14 BTW) son realizes his dad is short-tempered.
I do a LOT of communicating with my son. I love what I have learned here. I know my S's LL, I know how to validate him, I am positive with him, he knows God and is very spiritual.
We talk about how to manage our anger and what is appropriate, and the consequenses if he chooses violence. I AM going to stop this cycle. (although I don't know where it started--my F in Law is NOT this way). My H learned to bully somewhere--maybe I taught him?? Wow--there is a thought for ya!